RCAIDE.Library.Methods.Aerodynamics.Common.Drag.parasite_drag_wing

parasite_drag_wing#

parasite_drag_wing(state, settings, geometry)[source]#

Computes the parasite drag coefficient for wings accounting for segments and compressibility effects.

Parameters:

  • state (Data) –

    Flight conditions containing:
    • conditions.freestream.mach_numberfloat

      Freestream Mach number [unitless]

    • conditions.freestream.temperaturefloat

      Freestream static temperature [K]

    • conditions.freestream.reynolds_numberfloat

      Freestream Reynolds number per unit length [unitless/m]

  • settings (dict) –

    Aerodynamic analysis settings containing:
    • wing_parasite_drag_form_factorfloat

      Form factor for wing parasite drag [unitless]

  • geometry (Data) –

    Wing geometry containing:
    • tagstr

      Unique identifier for the wing

    • thickness_to_chordfloat

      Thickness-to-chord ratio [unitless]

    • areas.referencefloat

      Reference area of the wing [m²]

    • areas.wettedfloat

      Wetted area of the wing [m²]

    • transition_x_upperfloat

      Upper surface transition point as fraction of chord [unitless]

    • transition_x_lowerfloat

      Lower surface transition point as fraction of chord [unitless]

    • segmentsdict, optional
      Dictionary of wing segments containing:
      • thickness_to_chordfloat

        Thickness-to-chord ratio of segment [unitless]

      • chords.mean_aerodynamicfloat

        Mean aerodynamic chord of segment [m]

      • areas.referencefloat

        Reference area of segment [m²]

      • areas.wettedfloat

        Wetted area of segment [m²]

      • sweeps.leading_edgefloat

        Leading edge sweep angle of segment [radians]

    • chords.mean_aerodynamicfloat

      Mean aerodynamic chord of wing [m]

    • sweeps.leading_edgefloat

      Leading edge sweep angle of wing [radians]

Returns:

Results are stored in state.conditions.aerodynamics.coefficients.drag.parasite[wing.tag]

Return type:

None

Notes

This function calculates the parasite drag coefficient for wings using compressible mixed flat plate theory with form factor corrections. The calculation handles both segmented and non-segmented wings, accounting for different transition points on upper and lower surfaces.

Major Assumptions

  • Mixed laminar-turbulent boundary layer with specified transition points

  • Compressible flat plate skin friction correlation

  • Form factor accounts for airfoil thickness and sweep effects

  • Cubic spline blending smooths transition between subsonic and supersonic regimes

  • Segmented wings are analyzed segment by segment and area-weighted

Theory

For segmented wings, the total parasite drag is area-weighted:

\(C_{D,parasite} = \frac{\sum_{i=1}^{n-1} C_{D,i} \cdot S_{ref,i}}{S_{ref,total}}\)

where each segment’s drag coefficient is calculated using the compute_parasite_drag function.

For non-segmented wings, the drag is calculated directly:

\(C_{D,parasite} = \frac{C_{f,upper} + C_{f,lower}}{2} \cdot k_w \cdot \frac{S_{wet}}{S_{ref}}\)

where:

  • \(C_{f,upper}\) and \(C_{f,lower}\) are the skin friction coefficients

  • \(k_w\) is the form factor

  • \(S_{wet}\) and \(S_{ref}\) are the wetted and reference areas

Definitions

‘Form Factor’

Multiplier accounting for the increase in drag due to airfoil shape compared to a flat plate.

References

[1] Stanford AA241 Course Notes. http://aerodesign.stanford.edu/aircraftdesign/aircraftdesign.html

See also

RCAIDE.Library.Methods.Aerodynamics.Common.Drag.compute_parasite_drag, RCAIDE.Library.Methods.Aerodynamics.Common.Drag.compressible_mixed_flat_plate

compute_parasite_drag(re, mac_w, Mc, Tc, xtu, xtl, sweep_w, t_c_w, Sref, Swet, C)[source]#

Computes the parasite drag coefficient for a wing section using compressible mixed flat plate theory.

Parameters:

  • re (float) – Freestream Reynolds number per unit length [unitless/m]

  • mac_w (float) – Mean aerodynamic chord of wing section [m]

  • Mc (float) – Freestream Mach number [unitless]

  • Tc (float) – Freestream static temperature [K]

  • xtu (float) – Upper surface transition point as fraction of chord [unitless]

  • xtl (float) – Lower surface transition point as fraction of chord [unitless]

  • sweep_w (float) – Leading edge sweep angle [radians]

  • t_c_w (float) – Thickness-to-chord ratio [unitless]

  • Sref (float) – Reference area of wing section [m²]

  • Swet (float) – Wetted area of wing section [m²]

  • C (float) – Form factor coefficient [unitless]

Returns:

  • wing_parasite_drag (float) – Parasite drag coefficient [unitless]

  • k_w (float) – Form factor [unitless]

  • cf_w_u (float) – Upper surface skin friction coefficient [unitless]

  • cf_w_l (float) – Lower surface skin friction coefficient [unitless]

  • k_comp_u (float) – Upper surface compressibility factor [unitless]

  • k_comp_l (float) – Lower surface compressibility factor [unitless]

  • k_reyn_u (float) – Upper surface Reynolds number factor [unitless]

  • k_reyn_l (float) – Lower surface Reynolds number factor [unitless]

Notes

This function calculates the parasite drag coefficient for a wing section using compressible mixed flat plate theory with separate analysis of upper and lower surfaces. The form factor accounts for airfoil thickness and sweep effects.

Major Assumptions

  • Mixed laminar-turbulent boundary layer with different transition points

  • Compressible flat plate skin friction correlation

  • Form factor accounts for airfoil thickness and sweep effects

  • Cubic spline blending for transonic regime

  • Upper and lower surfaces are analyzed separately

Theory

The wing Reynolds number is:

\(Re_w = Re \cdot MAC\)

where \(Re\) is the freestream Reynolds number per unit length and \(MAC\) is the mean aerodynamic chord.

The skin friction coefficients are calculated separately for upper and lower surfaces:

\(C_{f,upper} = f(Re_w, M, T, x_{tu})\)

\(C_{f,lower} = f(Re_w, M, T, x_{tl})\)

The form factor for subsonic flow (M ≤ 1.0) is:

\(k_w = 1 + \frac{2C(t/c)\cos^2(\Lambda)}{\beta} + \frac{C^2\cos^2(\Lambda)(t/c)^2(1+5\cos^2(\Lambda))}{2\beta^2}\)

where:

  • \(\beta = \sqrt{1-(M\cos(\Lambda))^2}\) is the Prandtl-Glauert factor

  • \(\Lambda\) is the leading edge sweep angle

  • \(t/c\) is the thickness-to-chord ratio

For transonic flow, the form factor is blended using a cubic spline:

\(k_w = k_w \cdot h_{00}(M) + 1 \cdot (1-h_{00}(M))\)

The parasite drag coefficient is:

\(C_{D,parasite} = \frac{C_{f,upper} + C_{f,lower}}{2} \cdot k_w \cdot \frac{S_{wet}}{S_{ref}}\)

Definitions

‘Form Factor’

Multiplier accounting for the increase in drag due to airfoil shape compared to a flat plate.

‘Mixed Boundary Layer’

Boundary layer that transitions from laminar to turbulent flow at specified points.

References

[1] Stanford AA241 Course Notes. adg.stanford.edu

See also

RCAIDE.Library.Methods.Aerodynamics.Common.Drag.compressible_mixed_flat_plate, RCAIDE.Library.Methods.Utilities.Cubic_Spline_Blender